U.S. patent number 11,102,817 [Application Number 16/534,931] was granted by the patent office on 2021-08-24 for system and method for supporting bursty communications in wireless communications systems.
This patent grant is currently assigned to Huawei Technologies Co., Ltd.. The grantee listed for this patent is Huawei Technologies Co., Ltd.. Invention is credited to Mohamed Adel Salem, Jiayin Zhang.
United States Patent |
11,102,817 |
Zhang , et al. |
August 24, 2021 |
System and method for supporting bursty communications in wireless
communications systems
Abstract
A computer implemented method for operating an access node
includes: generating, by the access node, an initial block and a
time-dependent signal for transmission in a channel occupancy time
(COT) of a shared communications channel, the initial block
including a time-independent initial sequence that enables the
initial block to be transmitted over any slot in the COT, wherein
the time-dependent signal is transmitted after the initial block;
and transmitting, by the access node, the initial block and the
time-dependent signal in a first slot of the COT. An access node is
also described.
Inventors: |
Zhang; Jiayin (Shanghai,
CN), Salem; Mohamed Adel (Kanata, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Huawei Technologies Co., Ltd. |
Shenzhen |
N/A |
CN |
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Assignee: |
Huawei Technologies Co., Ltd.
(Shenzhen, CN)
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Family
ID: |
1000005759868 |
Appl.
No.: |
16/534,931 |
Filed: |
August 7, 2019 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20200053782 A1 |
Feb 13, 2020 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62716869 |
Aug 9, 2018 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W
74/002 (20130101); H04W 72/0446 (20130101); H04W
72/1205 (20130101); H04L 27/0006 (20130101); H04W
74/0816 (20130101) |
Current International
Class: |
H04L
27/00 (20060101); H04W 74/08 (20090101); H04W
72/04 (20090101); H04W 72/12 (20090101); H04W
74/00 (20090101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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105636221 |
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Jun 2016 |
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CN |
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106465411 |
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Feb 2017 |
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CN |
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107889114 |
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Apr 2018 |
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CN |
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Other References
3rd Generation Partnership Project; Technical Specification Group
Access Network; NR; Physical Channels and modulation (Release 15),
3GPP TS 38.211, V15.3.0, 93 Pages, Sep. 2018. cited by applicant
.
LG Electronics, "Physical layer design of DL signals and channels
for NR unlicensed operation", 3GPP TSG RAN WG1 Meeting #93, May
21-25, 2018, 4 Pages, R1-1806643, Busan, Korea. cited by applicant
.
Qualcomm Incorporated, "DL signals and channels for NR-U", 3GPP TSG
RAN WG1 Meeting #93, May 21-May 25, 2018, 10 Pages, R1-1807387,
Busan, Korea. cited by applicant .
Huawei et al., "Initial access in NR unlicensed", 3GPP TSG RAN WG1
Meeting #94, R1-1808062, Aug. 20-Aug. 24, 2018, 6 Pages,
Gothenburg, Sweden. cited by applicant.
|
Primary Examiner: Wang; Yaotang
Attorney, Agent or Firm: Slater Matsil, LLP
Parent Case Text
CROSS REFERENCE
This application claims priority to U.S. Provisional Patent
Application Ser. No. 62/716,869, filed Aug. 9, 2018, entitled
"System and Method for Supporting Bursty Communications in Wireless
Communications Systems", the contents of which are incorporated by
reference herein in their entirety.
Claims
What is claimed is:
1. A computer-implemented method for operating an access node, the
method comprising: generating, by the access node, an initial block
and a time-dependent signal for transmission in a channel occupancy
time (COT) of a shared communications channel, the initial block
including a time-independent initial sequence such that the initial
block is independent of system timing, the time-independent initial
sequence enabling the initial block to be transmitted over any slot
in the COT, wherein the time-dependent signal is transmitted after
the initial block; and transmitting, by the access node, the
initial block and the time-dependent signal in a first slot of the
COT.
2. The method of claim 1, wherein the time-independent initial
sequence comprises a demodulation reference signal (DMRS) for
control information.
3. The method of claim 2, wherein the DMRS for control information
is transmitted over a physical broadcast channel (PBCH).
4. The method of claim 2, wherein the DMRS for control information
is transmitted over a physical downlink control channel (PDCCH)
having a structure of control resource set (CORESET).
5. The method of claim 4, wherein the DMRS for control information
is a DMRS for one or more physical downlink control channels
(PDCCHs) in the CORESET at a beginning of the COT.
6. The method of claim 5, wherein the one or more PDCCHs are group
common (GC)-PDCCH in a common search space at a beginning of the
COT.
7. The method of claim 6, wherein the GC-PDCCH carries a COT
structure indication in one or more of a time domain and a
frequency domain.
8. The method of claim 1, wherein the initial block is transmitted
at the beginning of each of a plurality of downlink (DL) bursts
within the COT.
9. The method of claim 1, wherein the initial block identifies the
slot within which it is transmitted as a reference slot.
10. The method of claim 9, wherein the time-dependent signal is
time-dependent relative to a time of the reference slot.
11. The method of claim 1, wherein the initial block further
comprises control information configuring the COT.
12. The method of claim ii, wherein the control information
comprises at least one of an indicator of a duration of the COT, or
an indicator of a composition of the COT.
13. The method of claim 12, wherein the indicator of the
composition of the COT comprises a transmission type for each slot
of the COT.
14. The method of claim 11, wherein a relative slot index of the
slot where the initial block located is carried in a control
information field of the initial block.
15. The method of claim 14, further comprising adjusting, by the
access node, the relative slot index of the slot with a slot offset
associated with the COT.
16. The method of claim 1, wherein the shared communications
channel comprises a plurality of listen before talk (LBT) subbands,
and wherein at least one initial block is transmitted in a subset
of LBT subbands of the plurality of LBT subbands.
17. The method of claim 16, wherein transmitting the initial block
comprises transmitting the at least one initial block over each
subband of the plurality of subbands in which an LBT process is
successfully performed.
18. The method of claim 16, wherein different initial blocks are
transmitted over each carrier of a subset of carriers during a
common slot.
19. The method of claim 16, wherein the same initial block is
transmitted over each carrier of a subset of carriers during a
common slot.
20. The method of claim 1, further comprising: generating, by the
access node, a second initial block comprising a time-dependent
initial sequence and control information configuring the COT; and
transmitting the second initial block in at least one second slot
of the COT, the at least one second slot of the COT being later
than the first slot of the COT.
21. The method of claim 1, wherein the time-independent initial
sequence of the initial block comprises a plurality of duplicates
of a PBCH DMRS.
22. The method of claim 1, further comprising transmitting, by the
access node, a transmission in a slot during a downlink portion of
the COT, the transmission being scrambled in accordance with a
relative slot index of the slot.
23. An access node for use in a wireless network, comprising: a
transmitter; a processor; and a non-transitory computer-readable
medium containing instructions which, when executed by the
processor, cause the access node to: generate an initial block and
a time-dependent signal for transmission in a channel occupancy
time (COT) of a shared communications channel, the initial block
including a time-independent initial sequence such that the initial
block is independent of system timing, the time-independent initial
sequence enabling the initial block to be transmitted over any slot
in the COT, wherein the time-dependent signal is transmitted after
the initial block; and transmit the initial block and the
time-dependent signal in a first slot of the COT.
24. The access node of claim 23, wherein the time-independent
initial sequence comprises a demodulation reference signal (DMRS)
for control information.
25. The access node of claim 24, wherein the DMRS for control
information is transmitted over a physical broadcast channel
(PBCH).
26. The access node of claim 24, wherein the DMRS for control
information is transmitted over a physical downlink control channel
(PDCCH) having a structure of control resource set (CORESET).
27. The access node of claim 26, wherein the DMRS for control
information is a DMRS for one or more physical downlink control
channels (PDCCHs) in the CORESET at a beginning of the COT.
28. The access node of claim 27, wherein the one or more PDCCHs are
group common (GC)-PDCCH in a common search space at a beginning of
the COT.
29. The access node of claim 28, wherein the GC-PDCCH carries a COT
structure indication in one or more of a time domain and a
frequency domain.
30. The access node of claim 23, wherein the initial block is
transmitted at the beginning of each of a plurality of downlink
(DL) bursts within the COT.
31. The access node of claim 23, wherein the initial block
identifies the slot within which it is transmitted as a reference
slot.
32. The access node of claim 31, wherein the time-dependent signal
is time-dependent relative to a time of the reference slot.
33. The access node of claim 23, wherein the initial block further
comprises control information configuring the COT.
34. The access node of claim 33, wherein the control information
comprises at least one of an indicator of a duration of the COT, or
an indicator of a composition of the COT.
35. The access node of claim 34, wherein the indicator of the
composition of the COT comprises a transmission type for each slot
of the COT.
36. The access node of claim 33, wherein a relative slot index of
the slot where the initial block located is carried in a control
information field of the initial block.
37. The access node of claim 36, the instructions further causing
the access node to adjust the relative slot index of the slot with
a slot offset associated with the COT.
38. The access node of claim 23, wherein the shared communications
channel comprises a plurality of listen before talk (LBT) subbands,
and wherein at least one initial block is transmitted in a subset
of LBT subbands of the plurality of LBT subbands.
39. The access node of claim 38, wherein different initial blocks
are transmitted over each carrier of a subset of carriers during a
common slot.
40. The access node of claim 38, wherein the same initial block is
transmitted over each carrier of a subset of carriers during a
common slot.
41. The access node of claim 23, the instructions further causing
the access node to: generate a second initial block comprising a
time-dependent initial sequence and control information configuring
the COT; and transmit the second initial block in at least one
second slot of the COT, the at least one second slot of the COT
being later than the first slot of the COT.
42. The access node of claim 23, wherein the time-independent
initial sequence of the initial block comprises a plurality of
duplicates of a PBCH DMRS.
43. The access node of claim 23, the instructions further causing
the access node to transmit a transmission in a slot during a
downlink portion of the COT, the transmission being scrambled in
accordance with a relative slot index of the slot.
Description
TECHNICAL FIELD
The present disclosure relates generally to a system and method for
wireless communications, and, in particular embodiments, to a
system and method for supporting bursty communications in wireless
communications systems.
BACKGROUND
Developers of future wireless communications systems are looking in
a wide variety of areas in order to provide increased data rates to
meet the ever increasing demands of users. One such area involves
communications in unlicensed radio spectrum to increase available
bandwidth. However, operating in some portions of the unlicensed
radio spectrum may have a regulatory requirement for the
interference that the communicating devices may cause to other
communicating devices, as well as being able to tolerate
interference from other communicating devices.
As an example, operation on some portions of unlicensed radio
spectrum in Europe requires that a transmitting device perform
listen before talk (LBT) before it makes a transmission. In LBT,
the transmitting device has to listen to the communications channel
(or channels) to ascertain that the communications channel is idle
before it can transmit. If the communications channel is not idle,
the transmitting device cannot transmit. The uncertainty related to
the availability of the communications channel may present a
problem for communications systems with scheduled communications
because the communications generally have to be scheduled and at
least partially generated before the transmitting device is able to
determine if the communications channel is available. Therefore, if
the communications channel is unavailable, at least some of the
scheduled communications cannot take place and the communications
that has been generated is wasted. Therefore, there is a need for
systems and methods for ensuring fair and efficient usage of the
unlicensed spectrum.
SUMMARY
Example embodiments provide a system and method for supporting
bursty communications in wireless communications systems.
In accordance with an example embodiment, a computer-implemented
method for operating an access node comprises: generating, by the
access node, an initial block and a time-dependent signal for
transmission in a channel occupancy time (COT) of a shared
communications channel, the initial block including a
time-independent initial sequence that enables the initial block to
be transmitted over any slot in the COT, wherein the time-dependent
signal is transmitted after the initial block; and transmitting, by
the access node, the initial block and the time-dependent signal in
a first slot of the COT.
Optionally, in any of the preceding embodiments, the
time-independent initial sequence comprises a demodulation
reference signal (DMRS) for control information.
Optionally, in any of the preceding embodiments, the DMRS for
control information is transmitted over a physical broadcast
channel (PBCH).
Optionally, in any of the preceding embodiments, the DMRS for
control information is transmitted over a physical downlink control
channel (PDCCH) having a structure of control resource set
(CORESET).
Optionally, in any of the preceding embodiments, the DMRS for
control information is a DMRS for one or more physical downlink
control channels (PDCCHs) in the CORESET at a beginning of the
COT.
Optionally, in any of the preceding embodiments, the one or more
PDCCHs are group common (GC)-PDCCH in a common search space at a
beginning of the COT.
Optionally, in any of the preceding embodiments, the GC-PDCCH
carries a COT structure indication in one or more of a time domain
and a frequency domain.
Optionally, in any of the preceding embodiments, the initial block
is transmitted at the beginning of each of a plurality of downlink
(DL) bursts within the COT.
Optionally, in any of the preceding embodiments, the initial block
identifies the slot within which it is transmitted as a reference
slot.
Optionally, in any of the preceding embodiments, the time-dependent
signal is time-dependent relative to a time of the reference
slot.
Optionally, in any of the preceding embodiments, the initial block
further comprises control information configuring the COT.
Optionally, in any of the preceding embodiments, the control
information comprises at least one of an indicator of a duration of
the COT, or an indicator of a composition of the COT.
Optionally, in any of the preceding embodiments, the indicator of
the composition of the COT comprises a transmission type for each
slot of the COT.
Optionally, in any of the preceding embodiments, a relative slot
index of the slot where the initial block located is carried in the
control information field of the initial block.
Optionally, in any of the preceding embodiments, the method further
comprises
Optionally, in any of the preceding embodiments, adjusting, by the
access node, the relative slot index of the slot with a slot offset
associated with the COT.
Optionally, in any of the preceding embodiments, the shared
communications channel comprises a plurality of listen before talk
(LBT) subbands, and wherein at least one initial block is
transmitted in a subset of LBT subbands of the plurality of LBT
subbands.
Optionally, in any of the preceding embodiments, transmitting the
initial block comprises transmitting the at least one initial block
over each subband of the plurality of subbands in which an LBT
process is successfully performed.
Optionally, in any of the preceding embodiments, different initial
blocks are transmitted over each carrier of a subset of carriers
during a common slot.
Optionally, in any of the preceding embodiments, the same initial
block is transmitted over each carrier of a subset of carriers
during a common slot.
Optionally, in any of the preceding embodiments, the method further
comprises: generating, by the access node, a second initial block
comprising a time-dependent initial sequence and control
information configuring the COT; and transmitting the second
initial block in at least one second slot of the COT, the at least
one second slot of the COT being later than the first slot of the
COT.
Optionally, in any of the preceding embodiments, the
time-independent initial sequence of the initial block comprises a
plurality of duplicates of a PBCH DMRS.
Optionally, in any of the preceding embodiments, the method further
comprises transmitting, by the access node, a transmission in a
slot during a downlink portion of the COT, the transmission being
scrambled in accordance with a relative slot index of the slot.
In accordance with an example embodiment, an access node for use in
a wireless network comprises: a transmitter; a processor; and a
non-transitory computer-readable medium containing instructions
which, when executed by the processor, cause the access node to:
generate an initial block and a time-dependent signal for
transmission in a channel occupancy time (COT) of a shared
communications channel, the initial block including a
time-independent initial sequence that enables the initial block to
be transmitted over any slot in the COT, wherein the time-dependent
signal is transmitted after the initial block; and transmit the
initial block and the time-dependent signal in a first slot of the
COT.
Optionally, in any of the preceding embodiments, the
time-independent initial sequence comprises a demodulation
reference signal (DMRS) for control information.
Optionally, in any of the preceding embodiments, the DMRS for
control information is transmitted over a physical broadcast
channel (PBCH).
Optionally, in any of the preceding embodiments, the DMRS for
control information is transmitted over a physical downlink control
channel (PDCCH) having a structure of control resource set
(CORESET).
Optionally, in any of the preceding embodiments, the DMRS for
control information is a DMRS for one or more physical downlink
control channels (PDCCHs) in the CORESET at a beginning of the
COT.
Optionally, in any of the preceding embodiments, the one or more
PDCCHs are group common (GC)-PDCCH in a common search space at a
beginning of the COT.
Optionally, in any of the preceding embodiments, the GC-PDCCH
carries a COT structure indication in one or more of a time domain
and a frequency domain.
Optionally, in any of the preceding embodiments, the initial block
is transmitted at the beginning of each of a plurality of downlink
(DL) bursts within the COT.
Optionally, in any of the preceding embodiments, the initial block
identifies the slot within which it is transmitted as a reference
slot.
Optionally, in any of the preceding embodiments, the time-dependent
signal is time-dependent relative to a time of the reference
slot.
Optionally, in any of the preceding embodiments, the initial block
further comprises control information configuring the COT.
Optionally, in any of the preceding embodiments, the control
information comprises at least one of an indicator of a duration of
the COT, or an indicator of a composition of the COT.
Optionally, in any of the preceding embodiments, the indicator of
the composition of the COT comprises a transmission type for each
slot of the COT.
Optionally, in any of the preceding embodiments, a relative slot
index of the slot where the initial block located is carried in the
control information field of the initial block.
Optionally, in any of the preceding embodiments, the instructions
further cause the access node to adjust the relative slot index of
the slot with a slot offset associated with the COT.
Optionally, in any of the preceding embodiments, the shared
communications channel comprises a plurality of listen before talk
(LBT) subbands, and wherein at least one initial block is
transmitted in a subset of LBT subbands of the plurality of LBT
subbands.
Optionally, in any of the preceding embodiments, the instructions
cause the access node to transmit the initial block including
instructions that cause the access node to transmit the at least
one initial block over each subband of the plurality of subbands in
which an LBT process is successfully performed.
Optionally, in any of the preceding embodiments, different initial
blocks are transmitted over each carrier of a subset of carriers
during a common slot.
Optionally, in any of the preceding embodiments, the same initial
block is transmitted over each carrier of a subset of carriers
during a common slot.
Optionally, in any of the preceding embodiments, the instructions
further cause the access node to: generate a second initial block
comprising a time-dependent initial sequence and control
information configuring the COT; and transmit the second initial
block in at least one second slot of the COT, the at least one
second slot of the COT being later than the first slot of the
COT.
Optionally, in any of the preceding embodiments, the
time-independent initial sequence of the initial block comprises a
plurality of duplicates of a PBCH DMRS.
Optionally, in any of the preceding embodiments, the instructions
further cause the access node to transmit a transmission in a slot
during a downlink portion of the COT, the transmission being
scrambled in accordance with a relative slot index of the slot.
Practice of the foregoing embodiments enables a reduction in wasted
overhead arising from the determination that the communications
channel is unavailable because the communications is scheduled
referenced to a relative index, therefore, the communications that
have been scheduled do not need to be discarded should the
communications channel be unavailable. Instead, the scheduled
communications may simply be referenced to a different relative
index once the communications channel becomes available.
Practice of the foregoing embodiments also helps to improve
interference whitening performance by generating concurrent
communications with differing relative slot indices when different
cells of a single transmit-receive point are transmitting.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present disclosure, and
the advantages thereof, reference is now made to the following
description taken in conjunction with the accompanying drawings, in
which:
FIG. 1 illustrates an example wireless communications system
according to example embodiments described herein;
FIG. 2 illustrates a first timing diagram highlighting a pipeline
for scheduling and transmitting of a burst transmission in a 3GPP
LTE LAA compliant communications system;
FIG. 3 illustrates a second timing diagram highlighting a prior art
technique for pipelining the scheduling and transmitting of a burst
transmission in a communications system;
FIG. 4 illustrates a flow diagram of example operations occurring
in an access node according to example embodiments described
herein;
FIG. 5 illustrates a flow diagram of operations occurring in a UE
according to example embodiments described herein;
FIG. 6 illustrates a third timing diagram illustrating a technique
for pipelining the scheduling and transmitting of a burst
transmission utilizing an initial block to help reduce power
consumption and processing complexity in situations with LBT
failure according to example embodiments described herein;
FIG. 7 illustrates an example slot structure of a COT, highlighting
a SSS as an initial sequence according to example embodiments
described herein;
FIG. 8 illustrates an example slot structure of a COT, highlighting
a CORESET used to carry an initial sequence according to example
embodiments described herein;
FIG. 9A illustrates a wideband COT in a deployment utilizing CA
according to example embodiments described herein;
FIG. 9B illustrates a wideband COT in a deployment utilizing a
single wideband CC according to example embodiments described
herein;
FIG. 9C illustrates a wideband COT in a deployment utilizing a
single wideband CC, highlighting a failed LBT process in one of the
channels according to example embodiments described herein;
FIG. 10 illustrates an example slot structure of a COT,
highlighting full and simplified initial blocks according to
example embodiments described herein;
FIG. 11 illustrates an example slot structure of a COT,
highlighting multiple initial sequences in an initial block
according to example embodiments described herein;
FIG. 12A illustrates example COTs transmitted by spatial reuse (SR)
access nodes, highlighting the use of different relative slot
indices to improve inter-cell interference whitening in a
synchronous system when COTs start at the same time according to
example embodiments described herein;
FIG. 12B illustrates example COTs transmitted by SR access nodes,
highlighting the application of slot index offsets to relative slot
indices in order to align bursts according to example embodiments
described herein;
FIG. 13 illustrates example COTs transmitted by SR access nodes,
highlighting the use of different slot index offsets to facilitate
intra-cell SR transmissions to the same UE with unaligned
transmission start according to example embodiments described
herein;
FIG. 14 illustrates an example communication system according to
example embodiments described herein;
FIGS. 15A and 15B illustrate example devices that may implement the
methods and teachings according to this disclosure according to
example embodiments described herein;
FIG. 16 is a block diagram of a computing system that may be used
for implementing the devices and methods disclosed herein; and
FIG. 17 illustrates a flow diagram of example operations 1700
occurring in an access node performing a transmission that involves
a LBT failure according to example embodiments described
herein.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
The making and using of the disclosed embodiments are discussed in
detail below. It should be appreciated, however, that the present
disclosure provides many applicable inventive concepts that can be
embodied in a wide variety of specific contexts. The specific
embodiments discussed are merely illustrative of specific ways to
make and use the embodiments, and do not limit the scope of the
disclosure.
FIG. 1 illustrates an example wireless communications system 100.
Communications system 100 includes an access node 105 serving a
plurality of user equipments (UEs), including UEs 110, 112, 114,
and 116. Access node 105 establishes downlink and uplink
connections with the UEs. The downlink connections carry data from
access node 105 to the UEs and the uplink connections carry data
from the UEs to access node 105. Data carried over the downlink or
uplink connections may include data communicated between the UEs
and services (not shown) by way of a backhaul network. Wireless
access may be provided in accordance with one or more wireless
communications protocols, e.g., the Third Generation Partnership
Project (3GPP) Long Term Evolution (LTE), LTE Advanced (LTE-A),
Fifth Generation (5G) New Radio (NR), high speed packet access
(HSPA), IEEE 802.11, and so on. Although it is understood that
communications systems may employ multiple access nodes capable of
communicating with any number of UEs, only one access node and six
UEs are illustrated for simplicity.
In a first operating mode, communications to and from the plurality
of UEs go through access node 105. In second communications mode,
direct communication between UEs is possible. An example of the
second communications mode is the proximity services (ProSe)
operating mode standardized in 3GPP. Access nodes may also be
commonly referred to as Node Bs, evolved Node Bs (eNBs), next
generation (NG) Node Bs (gNBs), master eNBs (MeNBs), secondary eNBs
(SeNBs), master gNBs (MgNBs), secondary gNBs (SgNBs), network
controllers, control nodes, base stations, access points,
transmission points (TPs), transmission-reception points (TRPs),
cells, carriers, macro cells, femtocells, pico cells, and so on.
UEs may also be commonly referred to as mobile stations, mobiles,
terminals, stations, and the like. Access nodes may provide
wireless access in accordance with one or more wireless
communication protocols, e.g., LTE, LTE-A, 3GPP NR, HSPA, Wi-Fi
802.11a/b/g/n/ac, etc.
Communications taking place in communications system 100 may occur
over licensed spectrum, which is radio spectrum that is purchased
from or licensed by a regulatory body, granting the purchaser or
licensee exclusive use of the radio spectrum. Communications in
communications system 100 may also occur over unlicensed spectrum
that is generally freely available for use by approved
communications devices. Communications devices operating in
unlicensed spectrum typically share one or more communications
channels. The communications devices operating in the unlicensed
spectrum typically have to be able to tolerate interference from
other communications devices while not causing undue interference
to other communications devices. Communications system 100 may
support communications in both licensed and unlicensed
spectrum.
As discussed previously, in certain areas of the world, a listen
before talk (LBT) process is required before a transmission is made
in some portions of the unlicensed radio spectrum. In LBT, the
transmitting device has to listen to the communications channel (or
communications channels) to determine that the communications
channel is idle before it can transmit. The process of determining
if the communications channel is idle is part of a process commonly
referred to as contending for access to the communications channel.
As an example, if the transmitting device senses the communications
channel for a specified period of time and if the energy detected
on the communications channel is below a specified threshold (i.e.,
an energy detection threshold), the transmitting device will regard
the communications channel as idle and the transmitting device
continues with the communications channel contention process. If
the communications channel is not idle, the transmitting device
cannot transmit and the transmitting device may retry the
communications channel contention process, potentially at a later
time or in a different communications channel. Even if LBT
operation is not required by governmental regulation, LBT operation
is widely used to enable co-existence with widely deployed IEEE
802.11 compliant communications systems (commonly referred to as
WiFi systems). The specified period of time that the transmitting
device senses the energy on the communications channel is dependent
on the communications system. As an example, in The Third
Generation Partnership Project (3GPP) Long Term Evolution (LTE)
Licensed Assisted Access (LAA) and IEEE 802.11, the period of time
is a random number of time slots that may differ based on traffic
priority. A time slot (sometimes known as a "slot") is a duration
of time that is specified in a technical standard or by an operator
of the communications system, or is determined through
collaboration between communicating devices.
Bursty communications may be characterized by short periods of
intense communications traffic occurring within long periods of
silence. Bursty communications are considered to be a good
candidate for communicating on unlicensed spectrum because the
sparseness of the communications decreases the likelihood that the
communications channel is busy when a transmitting device has data
to transmit.
Transmission uncertainty presents a problem for communications
systems that utilize scheduled communications (such as
communications systems that are compliant with the 3GPP LTE family
of technical standards) because the communications have to be
scheduled in advance of the transmitting device determining
communications channel availability or after the transmitting
device successfully contended for the communications channel. If a
communication is scheduled in advance and the communications
channel is available, the transmission may take place as intended.
However, if the communications channel is unavailable, the work
associated with the scheduling of the transmissions is wasted
because the transmitting device is unable to transmit at the
intended times and frequencies. If the communication is scheduled
after successful contention for access to the communications
channel, the time involved with scheduling the communication adds
to the communication latency. Additionally, if the time required
for scheduling the communication is too long, another communicating
device may have begun accessing the communications channel during
that time, resulting in the communications channel no longer being
available.
FIG. 2 illustrates a first timing diagram 200 highlighting a
pipeline for scheduling and transmitting of a burst transmission in
a communications system. In the communications system, a
transmitting device, such as a gNB, schedules a channel occupancy
time (COT) 205 comprising two downlink (DL) transmission time
intervals (TTIs) (shown as DL #1 210 and DL #2 212) and two uplink
(UL) TTIs (shown as UL #1 214 and UL #2 216). A COT is defined as a
time period during which a device can have access to a given
channel without re-evaluating the availability of that channel. A
maximum COT (MCOT) is a maximum amount of time a device is allowed
to occupy the channel after obtaining access to the channel. In
general, a COT is less than or equal to MCOT.
As shown in FIG. 2, a transmission prepared for DL #1 210 is
scheduled for transmission in slot n+1, and is prepared for
transmission in the previous time slot n. In general, a slot is a
duration of time and is one of a variety of time domain resources
of a communications system. As an example, in a 3GPP LTE
communications system configured for frequency division duplexing
(FDD) operation, a slot is 0.5 ms in duration and comprises six or
seven orthogonal frequency division multiplexing (OFDM) symbols.
Furthermore, two slots make up a subframe, 10 subframes form a
frame, and a TTI is a subframe. In a 3GPP NR communications system,
a slot contains 14 OFDM symbols. Slots, mini-slots containing 1, 2,
4, or 7 OFDM symbols, or a combination thereof can be used for
scheduling. In 3GPP NR, a TTI can be any combination of slots,
mini-slots, etc., that are used for scheduling. Other
communications systems have other slot configurations. Other TTIs
are similarly prepared for transmission prior to their scheduled
transmissions. UL #1 214 is specified by information included in DL
#1 210, and UL #2 216 is specified by information included in DL #2
212. COT 205 comprises four slots. However, a COT, in general, can
include an arbitrary number of slots (unless restricted by
technical standard or deployment setting).
If a LBT process performed by the transmitting device for slot n+1
determines that the communications channel is unavailable for slot
n+1 (shown as LBT failure 220) the transmitting device discards the
transmission that was prepared for DL #1 210. The transmission
cannot be reused in a later slot because the signals generated for
slot n+1 are time dependent. Furthermore, remaining time is not
sufficient for generating signals for DL #1 in slot n+1. The
transmission prepared for DL #1 210 is delayed for a time period
because it is rescheduled by a media access control (MAC) layer
entity and regenerated by a physical (PHY) layer entity (shown as
DL #1*222). The rescheduling of the transmission prepared for DL #1
210 may be in accordance with a hybrid automatic repeat requested
(HARQ) retransmission procedure. Because the transmission prepared
for DL #1 210 was not transmitted, information about UL #1 214 was
not sent and slot n+3 cannot be used for the intended uplink grant
(shown as block 230). Additionally, due to a long time gap between
the downlink burst (DL #2 212) and the uplink burst (UL #2 216),
another communications system, such as a co-inhabiting WiFi system,
may obtain access to the communications channel and block the
transmission prepared for UL #2 216. Furthermore, the computational
resources and processing capability of the transmitting device are
wasted because packets that have been prepared for transmission
will be discarded due to the unavailability of the communications
channel. Under heavy network load scenarios, the likelihood of the
communications channel being busy increases, therefore, the
likelihood of transmissions prepared for particular slots being
discarded also increases, resulting in increased computational
resource and processing capability waste.
FIG. 3 illustrates a second timing diagram 300 highlighting a prior
art technique for pipelining the scheduling and transmitting of a
burst transmission in a communications system. A transmitting
device, such as a gNB, schedules a COT 305 comprising two DL TTIs
and two UL TTIs (shown as DL #1 310, DL #2 312, UL #1 314, and UL
#2 316, respectively). A LBT process performed by the transmitting
device for slot n+1 determines that the communications channel is
unavailable for slot n+1 (shown as block 320). However, the
entirety of COT 305 is deferred until the communications channel is
available. As shown in FIG. 3, the communications channel becomes
available for slot n+2 and COT 305 is transmitted in its entirety
starting at slot n+2. However, due to a limited amount of time
remaining after the transmitting device determines that the
communications channel is unavailable for slot n+1, the
transmitting device has to regenerate the signals of DL #1 310 for
slot n+2 in a very short period of time, which increases the
hardware requirements on the transmitting device. Otherwise,
signals that are completely independent of time are used for the
entirety of COT 305, which results in compromised interference
whitening arising from interactions with the transmission of COTs
using time independent signals by neighboring cells. Some
communications systems, such as WiFi, trade off increased preamble
length in order to maintain a high level of interference whitening
from neighboring cells.
According to an example embodiment, a time independent initial
block (or initial blocks) is included in a COT. The initial block
is used for burst identification or slot identification. The
initial block may also be referred to as an identification signal
or identification block. The initial block is independent of an
absolute time, such as a system time, absolute slot index, absolute
mini-slot index, etc. In general, an initial block is independent
of a slot index, subframe index, or symbol index that is itself,
relative to a cell specific synchronization signal. Nevertheless,
when multiple initial blocks are transmitted in the time domain
within a COT, they are still dependent on their relative slot
indices with respect to the reference slot, subframe, or symbol of
that COT. The inclusion of the time independent initial block in
the COT addresses issues, such as the interruption of a COT
transmission due to LBT failure and the discarding of transmissions
prepared for TTIs, the large packet delay due to HARQ rescheduling,
the waste of computational and processing resources, the high
hardware requirement associated with processing delays, and the
degraded interference whitening performance. In an embodiment, the
initial block includes a predefined signal or sequence to help
ensure reliable detection by receiving devices. The predefined
signal or sequence is referred to as an initial sequence. The
initial sequence may be defined by a technical standard, operator
of the communications system, or agreed upon by the communicating
devices through collaboration.
In an embodiment, the initial block also includes downlink control
information included in a downlink control field. The downlink
control information includes configuration information for a
subsequent COT. As an example, the configuration information
includes at least the remaining duration of the COT (e.g., a number
of slots or mini-slots), and the composition of the COT (e.g., a
downlink transmission type, an uplink transmission type, or an
unknown or flexible transmission type for each slot or mini-slot of
the COT).
According to an example embodiment, a transmitting device transmits
a time independent initial block (or initial blocks) in a COT. The
inclusion of a time independent initial block eliminates the need
to regenerate an initial block that is time dependent if the
communications channel is unavailable and the COT has to be
rescheduled. The COT may be a downlink only COT or a shared
downlink and uplink COT with one or more switch points. A switch
point is when, in a shared COT, a downlink portion of the shared
COT becomes an uplink portion, and vice versa. In an embodiment,
the initial block includes an initial sequence that is known to the
UE. In an embodiment, the initial block is included at or near the
beginning of the COT. In an embodiment, the initial block is
included at or near the beginning of at least some of the downlink
portions of the COT. In an embodiment, the initial block is
included at or near the beginning of at least some of the downlink
portions of the shared COT, if multiple switch points are
configured. The placement of the initial block at or near the
beginning of the COT enables earlier detection of the COT (when
compared to the initial block being placed at the middle or end of
the COT). Additionally, after the detection of the initial block,
the UE begins blind detection of the PDCCH. In an embodiment, the
initial block also includes a DL control field that includes
configuration information of the COT. In an embodiment, the
transmit DL portions (e.g., DL TTIs) of the COT are scrambled using
scrambling sequences that are based on a slot index that is
relative to the start of the COT. In an embodiment, the receive UL
portions (e.g., UL TTIs) of the COT are scrambled using scrambling
sequences that are based on a slot index that is relative to the
start of the COT. The use of scrambling sequences that are based on
the slot index that is relative to the start of the COT also
eliminates the need to regenerate the signals for the transmit DL
portions and the receive UL portions should the COT be
rescheduled.
It will be understood that, in this embodiment, a UE only detects
the initial block to determine the beginning of the COT. After
detecting the COT, the UE performs blind detection of the PDCCH for
the duration of the COT. After the end of the COT, the UE resumes
detecting only the initial block to determine the presence of the
next COT.
According to an example embodiment, a receiving device receives a
time independent initial block (or initial blocks) and determines
the beginning of a COT. In an embodiment, receive DL portions
(e.g., DL TTIs) of the COT are scrambled using scrambling sequences
that are based on a slot index that is relative to the start of the
COT. In an embodiment, the transmit UL portions (e.g., UL TTIs) of
the COT are scrambled using scrambling sequences that are based on
a slot index that is relative to the start of the COT. Although the
discussion focuses on slot index and indices, the example
embodiments presented herein are also operable with mini-slot or
symbol index and indices. Therefore, the discussion of slot indices
should not be construed as being limiting to the scope of the
example embodiments.
FIG. 4 illustrates a flow diagram of example operations 400
occurring in an access node. Operations 400 may be indicative of
operations occurring in an access node as the access node
participates in communications with a UE. As an illustrative
example, the access node is participating in communications (e.g.,
bursty communications) with the UE. The bursty communications
includes downlink transmissions only or both downlink and uplink
transmissions. The communications occurs in licensed or unlicensed
spectrum.
Operations 400 begin with the access node contending for access to
a communications channel (block 405). The access node may contend
for access to the communications channel by measuring energy on the
communications channel for a specified amount of time and if the
measured energy is below a threshold, the access node determines
that the communications channel is idle and obtains access to the
communications channel. If the measured energy is above the
threshold, the access node determines that the communications
channel is not idle and not available for access. Although the
discussion focusses on a single communications channel, the example
embodiments presented herein are operable with more than one
communications channels, with the communications channel being
contiguous in frequency or non-contiguous in frequency, with or
without carrier aggregation, with or without channel bonding, and
so on. Therefore, the discussion of a single communications channel
should not be construed as being limiting to the scope of the
example embodiments.
The access node performs a check to determine if access to the
communications channel was obtained (block 407). If access to the
communications channel was not obtained, the access node returns to
block 405 to continue contending for access to the communications
channel. The access node may wait for a period of time before it
repeats the contention for access to the communications
channel.
If the access node was able to obtain access to the communications
channel, the access node generates an initial block (block 409).
The initial block is independent of the absolute slot index
determined during downlink synchronization. In other words, the
initial block is not based on an absolute slot index of a slot
where the access node intends to transmit the initial block. In an
embodiment, the initial block includes a predefined signal or a
sequence (referred to as an initial sequence) that is known to the
UE. The initial block may also include downlink control information
included in a downlink control field. The downlink control
information includes configuration information for a following COT.
The configuration information includes at least the remaining
duration of the COT (e.g., a number of slots or mini-slots or
symbols), and the composition of the COT (e.g., downlink
transmission, uplink transmission, or unknown transmission for each
slot or mini-slot of the COT). In an embodiment, the initial block
is generated by the access node prior to or during the access node
contending for the communications channel. The access node
transmits the initial block (block 411).
The access node transmits downlink transmission portions of COT
with scrambling based on a slot index relative to the slot where
the initial block was transmitted (block 413). In other words, the
downlink transmissions made by the access node are scrambled based
on a slot index relative to the start of the COT. The access node
receives uplink transmissions of COT with scrambling based on a
slot index relative to the slot where the initial block was
transmitted (block 415). In other words, the uplink transmissions
received by the access node are scrambled based on a slot index
relative to the start of the COT. In a situation where there are
multiple switch points in the COT and where the access node
transmitted a single initial block at or near the beginning of the
COT, the access node may continue to transmit downlink bursts
within the COT with the relative slot indices relative to the slot
where the single initial block was transmitted. In a situation
where there are multiple switch points in the COT and where the
access node transmitted initial blocks at or near the beginning of
at least some of the downlink portions, the access node may
continue to transmit downlink bursts within the COT with the
relative slot indices relative to the slot wherein the most recent
initial block was transmitted. The transmission of a plurality of
initial blocks allows the access node to change the structure of
the COT as well as send indications of the changed COT structure,
in the downlink control field, for example.
In an embodiment, when a COT comprises multiple switch points, the
access node may transmit initial blocks at or near the beginning of
at least some of the downlink portions. The slot indices used for
the downlink portions are relative to the slot wherein the most
recent initial block was transmitted, and the slot indices used for
the uplink portions are the absolute slot indices of the slots
including the respective uplink portions. In other words, the
downlink portions of a COT utilize slot indices that are relative
to the slots where the most recent initial block was transmitted,
and the uplink portions of the COT utilize absolute slot
indices.
FIG. 5 illustrates a flow diagram of operations 500 occurring in a
UE. Operations 500 may be indicative of operations occurring in a
UE as the UE participates in communications with an access node. As
an illustrative example, the UE is participating in communications
(e.g., bursty communications) with the access node. The bursty
communications includes downlink transmissions only or both
downlink and uplink transmissions. The communications occurs in
licensed or unlicensed spectrum.
Operations 500 begin with the UE receiving and detecting an initial
block (block 505). Because the initial block includes a predefined
signal or a sequence that is known to the UE, the UE is able to
readily detect the initial block. In general, the UE attempts to
receive and detect the initial block at every possible start point
of a COT until the UE detects the initial block. The UE determines
a start of the COT (block 507). The UE regards a slot where it was
able to detect the initial block as the start of the COT, for
example. As an illustrative example, if the initial block is
detected in slot # n, then slot # n will be considered as a
reference slot and the signals and sequences used in the
transmissions and receptions will be relative to the reference
slot. As an example, the transmissions and receptions are scrambled
with a sequence generated relative to a slot index relative to the
slot where the initial block was detected. The UE receives downlink
portions of the COT with scrambling based on a slot index relative
to the slot where the initial block was detected (block 509). The
UE transmits uplink portions of the COT with scrambling based on a
slot index relative to the slot where the initial block was
detected (block 511). Prior to transmitting an uplink portion of
the COT, the UE may contend for access to the communications
channel.
If the UE received the initial block but was not able to
successfully decode the control information field therein, the UE
still has knowledge of a downlink transmission portion of the COT
and can continue to monitor the shared communications channel for
an additional initial block with associated control information
field. The UE can continue the monitoring until it is able to
receive and decode the initial block with associated control
information field or until a maximum time (as defined by an MCOT,
for example) has elapsed.
FIG. 6 illustrates a third timing diagram 600 illustrating a
technique for pipelining the scheduling and transmitting of a burst
transmission utilizing an initial block to help reduce power
consumption and processing complexity in situations with LBT
failure. Timing diagram 600 displays a COT 605 including two DL
TTIs (shown as DL #1 610 and DL #2 612) and two UL TTIs (shown as
UL #1 614, and UL #2 616). COT 605 also includes an initial block
620 that is transmitted at the beginning or near the beginning of
COT 605. As shown in FIG. 6, initial block 620 and DL #1 610 are
transmitted in slot n+1 625, DL #2 612 is transmitted in slot n+2
630, and so on. A UE receiving and detecting initial block 620
regards slot n+1 625 as a reference slot and assigns a relative
slot index zero to the slot 625. Slot n+2 630 is one slot after the
reference slot and therefore is assigned relative slot index one.
Remaining slots of COT 605 are similarly numbered, all relative to
the reference slot. In a situation where a downlink portion starts
within a slot duration with a mini-slot, the slot that includes the
mini-slot is considered to be the reference slot.
According to an example embodiment, the initial sequence of the
initial block is independent of slot index. In an embodiment, the
content of the downlink control field, as well as the scrambling of
the downlink control field and a demodulation reference signal
(DMRS) of the downlink control field (if not used as the initial
sequence) is dependent on the relative slot index. In an
embodiment, the initial sequence is generated a priori. As an
example, a secondary synchronization signal (SSS) as defined in
3GPP LTE and 3GPP New Radio (NR) is used for the initial sequence.
A SSS sequence in 3GPP NR is defined as follows:
.function..times..function..times..times..times..function..times..functio-
n..times..times..times..times..ltoreq.< ##EQU00001## where
N.sub.ID.sup.(1).di-elect cons.{0, 1, . . . , 355} and
N.sub.ID.sup.(2).di-elect cons.{0, 1, 2}. A physical cell
identifier may be obtained according to
N.sub.ID.sup.cell=3N.sub.ID.sup.(1)+N.sub.ID.sup.(2). The SSS is
independent of slot index and can be generated a priori. A UE can
reuse existing SSS detection hardware and algorithm, which helps
simplify implementation. Additionally, the number of available SSS
sequences is sufficiently large to avoid false detection of initial
blocks of neighboring cells. Examples of sequences that are
independent of slot index include SSS, primary synchronization
signal (PSS), DMRS defined for a physical broadcast channel (PBCH),
PDCCH DMRS, DMRS with a predefined slot index (e.g., slot index
zero but other values are possible), short training and long
training sequences as specified in IEEE 802.11 technical standards,
and so on.
The use of a SSS sequence for an initial sequence offers a variety
of benefits, including: reliable detection performance;
independence of absolute slot index; sufficient number of unique
sequences to differentiate from neighbor cells; will not increase
synchronization signal block (SSB) false detection for initial
access UEs; and reuses existing detection hardware. The design of
the control information field allows for independence of slot index
and sufficient capacity to accommodate information bits.
FIG. 7 illustrates an example slot structure of a COT 700,
highlighting a SSS as an initial sequence. In slot n 705, the
initial block is transmitted in sixth and seventh OFDM symbols 707
after an access node successfully contends for access to a 20 MHz
communications channel (shown as occurring during first five OFDM
symbols 710 of slot n 705). The initial block being transmitted in
sixth and seventh OFDM symbols 707 is for illustrative purposes
only. The duration of the initial block is dependent upon the
content of the initial block. Hence, the illustration of the two
symbol long initial block should not be construed as being limiting
to the scope of the example embodiments. The SSS (i.e., the initial
sequence) of length 127 is transmitted in a total of 14 physical
resource blocks (PRBs) 715. Discussion of the initial block being
transmitted in sixth and seventh OFDM symbols 707, and the length
127 initial sequence occupying 14 PRBs around the center frequency
of the OFDM symbol are for illustrative purposes only; the initial
block may be transmitted in a different OFDM symbol, and the
initial sequence may be of different length and occupy a different
number of PRBs. The channel contention may occur prior to slot n
705.
The downlink control field carries the configuration of COT 705 and
may be multiplexed with the initial sequence in a frequency
division multiplexed (FDM) manner or a time division multiplexed
(TDM) manner (such as PRBs 720 and 722). A DMRS defined for a PBCH
in 3GPP TS 38.211 may be used in each PRB of the control
information field. As shown in FIG. 7, a DMRS is carried in a tone,
such as subcarrier 724. As another example, a DMRS defined for a
PDCCH may be used in each PRB of the control information field with
the slot index set to a predefined value, e.g., zero.
It is shown in FIG. 7 that all or part of 12 PRBs remaining in the
same OFDM symbol as the initial sequence may be used to carry the
control information field of the initial block (e.g., PRBs 720 and
721). Within each PRB, such as PRB 730, three subcarriers (e.g.,
subcarrier 724) are used for DMRS. A similar resource mapping and
sequence generation used for PDCCH DMRS, defined in 3GPP TS38.211,
may also be used assuming a predefined slot index, e.g., slot index
zero. The initial blocks may also have additional OFDM symbols for
the control information field (e.g., PRB 722). If other subcarrier
spacings or bandwidths are adopted, the number of PRBs used by the
initial sequence and control information fields may be different
from what is shown in FIG. 7.
As shown in FIG. 7, the initial sequence (SSS in PRBs 715) is
located at the center of the communications channel by default.
However, the access node can also configure the position of the
initial sequence in system information, e.g., a PBCH, remaining
system information (RMSI), or other system information (OSI), or
through UE specific radio resource control (RRC) signaling. In
addition to the position of the initial sequence, other parameters
of the initial block may be configured, including: a number of OFDM
symbols in the time domain, a number of physical resource blocks
(PRBs) in the frequency domain, sub-carrier spacing, and so on, for
example. The configuration of the initial block may be included
with the configuration of bandwidth parts (BWPs).
In an embodiment, the initial block also includes a parameter for a
relative slot index of a current slot. The information, along with
other downlink control information, may be encoded together as a
single physical layer control channel (such as a PBCH) or encoded
as an individual DCI with the resource mapping of a PDCCH in a
common search space.
According to an example embodiment, a wideband control resource set
(CORESET) is configured at the first or several slots or mini-slots
of a COT. The DMRS of each PRB within the CORESET are configured in
a similar manner as the DMRS of PBCH or DMRS of PDCCH with
predefined slot index from a resource mapping and scrambling
perspective, as defined in 3GPP TS 38.211, which are independent of
slot index. The DMRS sequence in the CORESET of the first slot or
mini-slot of the COT serves as the initial sequence. Some of the
PDCCH candidates in the CORESET may be used to carry the downlink
control information, as described previously. The remainder of the
CORESET in the COT that is not carrying the initial block follows
the CORESET configuration for CORESETs as specified in 3GPP NR and
uses the PDCCH DMRS. In other words, the remainder of the CORESET
within the COT does not necessarily have to be wideband. The
CORESET carrying initial block(s) and not carrying initial block
may have different configuration. For the remainder of the CORESET
carrying the initial block, the UE will assume that the DMRS of the
CORESET appears in each PRB even if some PDCCH candidates in the
CORESET are not used.
The use of a CORESET to carry the initial block offers a variety of
benefits, including: saving individual OFDM symbols for initial
sequences and the DMRS sequences in the CORESET be shared with
PDCCH search spaces for data channel scheduling; the initial block
is independent of slot index; a PDCCH detection procedure is used
(i.e., no specific initial block detection procedure is needed); a
sufficient number of sequences are available to differentiate from
neighbor cells; and does not increase SSB false detection for
initial access UEs.
In an embodiment, the CORESET does not include a SSS to be used as
an initial sequence. Instead, the DMRS sequence is used as an
initial sequence. The remainder of the PRBs in the signal may be
used to convey control information, in accordance with the PBCH
structure. As an example, the initial sequence and the control
information may be coded together.
In an embodiment, the initial sequence of the initial block is a
separate sequence that is independent of slot index, such as SSS,
PSS, short training and long training sequences as specified in
IEEE 802.11 technical standards, and so on. In an embodiment, the
initial sequence of the initial block is a DMRS, such as a PBCH
DMRS, a PDCCH DMRS, a DMRS with a predefined slot index (e.g., slot
index zero but other values are possible), and so on. In an
embodiment, the downlink control field follows the structure of a
PDCCH. In an embodiment, the downlink control field follows the
structure of a PBCH.
FIG. 8 illustrates an example slot structure of a COT Boo,
highlighting a CORESET used to carry an initial sequence. In slot n
805, PBCH DMRS (such as PBCH DMRS 807) of a CORESET 810 carried in
OFDM symbol 815 serves as the initial sequence. PRBs (such as PRBs
820 and 822) are used to carry downlink control information for COT
800. A CORESET carried in OFDM symbol 830 of slot n+1 835 may be a
regular CORESET conforming to PDCCH DMRS mapping rules. In an
embodiment, a CORESET carrying the initial blocks, such as CORESET
810, may be configured by system information, which may be signaled
by PBCH, RMSI, OSI, or RRC signaling. The configuration of the
CORESET carrying the initial blocks may also be signaled along with
BWP configuration. Prior to a UE detecting a PDCCH with the
assumption of a regular CORESET configuration, the UE may assume a
CORESET configuration that includes the CORESET carrying an initial
block.
According to an example embodiment, in a wideband deployment, one
initial block of a plurality of initial blocks is transmitted on
each subband where a LBT process succeeds. When an access node is
configured for wideband transmission, such as through carrier
aggregation (CA) or single wideband component carrier (CC), one
initial block of a plurality of initial blocks is transmitted on
each subband where a LBT process succeeds. A UE may obtain the
actual transmission bandwidth of the COT by detecting the existence
of initial blocks on each subband. If CA is used, the initial block
on each CC will be different because each CC has its own cell
identifier. If single wideband CC is used, the initial block is
duplicated on each subband assuming the same cell identifier is
used.
The reliability of detection of the initial block is increased by
transmitting multiple initial blocks or sequences in the frequency
domain, the time domain, or both the frequency and time domains.
The simplified initial block reduces communications overhead in a
situation when multiple initial blocks are transmitted.
FIG. 9A illustrates a wideband COT 900 in a deployment utilizing
CA. As shown in FIG. 9A, COT 900 comprises four CCs, such as CC 905
and CC 907. Each of the four CCs carries a different initial block,
such as initial blocks 910 and 912, because each CC has its own
cell identifier. FIG. 9B illustrates a wideband COT 930 in a
deployment utilizing a single wideband CC. COT 930 comprises four
bonded channels. Each of the four channels carries a copy of an
initial block, such as initial blocks 935 and 937. In an
alternative embodiment, in a wideband COT deployed using a single
wideband CC comprising a plurality of bonded channels, each channel
in a subset of the plurality of bonded channels will carry a copy
of the initial block. In other words, some of the bonded channels
will carry a copy of the initial block. At a UE receiving the
wideband COT, when the UE detects the initial block on any one of
the channels, the UE will be able to obtain full knowledge of the
wideband COT. In this deployment, the UE is not required to detect
the initial block on each channel, therefore, the computational
requirements on the UE is reduced. Reduced computational
requirements may enable the use of a lower complexity UE. FIG. 9C
illustrates a wideband COT 960 in a deployment utilizing a single
wideband CC, highlighting a failed LBT process in one of the
channels. As shown in FIG. 9C, COT 960 comprises four bonded
channels, however, channel 965 is determined to be unavailable
during a LBT process and is not used in COT 960. Hence, COT 960
comprises the three bonded channels that are available. Each of the
three channels carries a copy of an initial block, such as initial
blocks 970 and 972. Because channel 965 is unavailable, the initial
block is not transmitted in resources 974 of channel 965.
In a situation when there are multiple slots or mini-slots in the
COT, the access node may transmit an initial block from a plurality
of initial blocks at the beginning of several or all slots or
mini-slots. The presence of the plurality of initial blocks
provides additional reliability if some UEs miss early initial
blocks or are not configured to monitor initial blocks at every
possible start point. The relative slot index and the COT structure
in the initial blocks may be updated by the access node according
to the slot where the initial blocks are transmitted. If a UE
detects multiple initial blocks, the UE will update based on a most
recently received version of the initial block. In order to save
communications overhead, it is possible to define a simplified
version of the initial blocks, which includes only a portion of the
downlink control information included in the full initial blocks,
for example. As an example, the simplified initial blocks include
only a relative slot index of the current slot in the control
information field, along with the initial sequence. Alternatively,
a simplified version of the initial block includes only the initial
sequence.
The access node may transmit the simplified initial block in one or
more slots after the one or more slots carrying the full initial
blocks within the COT. The initial sequence in the full initial
block and the simplified initial block may be different in order to
allow the UE to recognize the different initial blocks. The
different initial block formats may also be distinguished by
different scrambling sequences or radio network temporary
identifier (RNTI) on the cyclic redundancy check (CRC) of the
downlink control information following the initial sequence.
FIG. 10 illustrates an example slot structure of a COT 1000,
highlighting full and simplified initial blocks. COT 1000 comprises
six slots, slots n through n+5. As shown in FIG. 10, full initial
blocks 1020 are transmitted in slots n 1005 and n+1 1007, and
simplified initial blocks 1025 are transmitted in slots n+2 1009,
n+3 1011, n+4 1013, and n+5 1015. As discussed previously, the
simplified initial blocks may include a reduced version of the
downlink control information included in the full initial blocks.
Although COT 1000 is shown to include two instances of the full
initial blocks and four instances of the simplified initial blocks,
there are no limitations on the number of full initial blocks and
simplified initial blocks in any particular COT. Furthermore, every
slot of COT 1000 is shown to include an initial block. However, it
is not required that every slot in a COT include an initial block,
either full initial block or simplified initial block.
Additionally, in a situation when a COT includes multiple CCs, a
first subset of the CCs may convey full initial blocks and a second
subset of the CCs may convey simplified initial blocks. Also, the
CCs of the first subset and the second subset can change for
different slots or mini-slots.
In a situation when smaller subcarrier spacing (SCS) is adopted,
such as 15 kHz or 30 kHz, the initial sequence may be duplicated
from specific unit sequences, such as a SSS, within the carrier
bandwidth and repeated multiple times. The coverage or reliability
of the initial sequence may be improved with increased transmit
power within the signal bandwidth. FIG. 11 illustrates an example
slot structure of a COT 1100, highlighting multiple initial
sequences in an initial block. As shown in FIG. 11, OFDM symbol
1110 of slot n 1105 of COT 1100 conveys an initial block. The
initial block includes at least two instances of an initial
sequence, SSS 1120 and 1122. Each instance of the initial sequence
may have smaller bandwidth than a single initial sequence. However,
the initial sequence instances may be spread apart within the
frequency domain to increase frequency diversity, for example.
According to an example embodiment, the initial sequence of the COT
is independent of the absolute slot index, while any remaining
sequences of the COT is based on a relative slot index, relative to
the start of the COT. The remaining sequences, e.g., the DMRS of
the PDCCH, PDSCH, or CSI-RS, are based on the relative slot index
of the slot or mini-slot where the initial sequence is transmitted.
The relative slot index is relative to the start of the COT.
Because the remaining sequences are based on the relative slot
index, the signals are independent of the absolute index obtained
from downlink synchronization. The generated signals may be
buffered when a LBT failure occurs and reused at a later slot,
instead of being discarded. Hence, computation resources of the
transmitting device are saved.
In an example where scrambling sequences similar to those defined
in 3GPP TS 38.211 are used, the initial number (or seed) used for
initializing the pseudo-random number generator of the scrambling
sequences are expressible as:
DMRS of PDCCH--
c.sub.init=(2.sup.17(14n.sub.s.sup..mu.+l+1)(2N.sub.ID+1)+2N.sub.ID)mod
2.sup.31;
DMRS or phase tracking reference signal (PTRS) of PDSCH--
c.sub.init=(2.sup.17(14n.sub.s.sup..mu.+l+1)(2N.sub.ID.sup.n.sup.SCID+1)+-
2N.sub.ID.sup.n.sup.SCID)mod 2.sup.31; or
CSI-RS--
c.sub.init(2.sup.10(14n.sub.s.sup..mu.+l+1)(2n.sub.ID+1)+n.sub.I-
D)mod 2.sup.31.
In an UL reception, the access node descrambles the DMRS of a
physical uplink control channel (PUCCH) format 2 and DMRS or PTRS
of PUSCH in a target slot or mini-slot using its relative slot
index. Assuming that scrambling sequences similar to those defined
in 3GPP TS 38.211 are used, the initial number (or seed) used for
initializing the pseudo-random number generator of the scrambling
sequences are expressible as:
DMRS of PUCCH format 2--
c.sub.init=(2.sup.17(14n.sub.s.sup..mu.+l+1)(2N.sub.ID.sup.0+1)+2N.sub.ID-
.sup.0)mod 2.sup.31;
DMRS or PTRS of PUSCH without transform precoding--
c.sub.init=(2.sup.17(N.sub.symb.sup.slotn.sub.s.sup..mu.+l+1)(2N.sub.ID.s-
up.n.sup.SCID+1)+2N.sub.ID.sup.n.sup.SCID+n.sub.SCID)mod 2.sup.31;
or
DMRS or PTRS of PUSCH with transform precoding--
c.sub.init=(2.sup.17(14n.sub.s.sup..mu.+l+1)(2N.sub.ID+1)+2N.sub.ID)mod
2.sup.31.
Additionally, group and sequence hopping for PUCCH format 0, 1, 3,
and 4 are as follows:
Group hopping of PUCCH--
f.sub.gh=(.SIGMA..sub.m=0.sup.72.sup.mc(8(2n.sub.s.sup..mu.+n.sub.hop)+m)-
)mod 30 f.sub.ss=n.sub.ID mod 30 v=0
Sequence hopping of PUCCH-- f.sub.gh=0 f.sub.ss=n.sub.ID mod 30;
v=c(2n.sub.s.sup..mu.+n.sub.hop)
Cyclic shift hopping of PUCCH--
.alpha..times..pi..times..function..mu.'.times..times.
##EQU00002##
Group hopping of sounding reference symbol (SRS)--
f.sub.gh(n.sub.s.sup..mu.,l')=(.SIGMA..sub.m=0.sup.7c(8(n.sub.s.sup..mu.N-
.sub.symb.sup.slot+l.sub.0+l')+m)2.sup.m)mod 30; or v=0
Sequence hopping of SRS--
.function..mu.'.function..mu..times.'.gtoreq..times. ##EQU00003##
In the expressions presented above, the term n.sub.s.sup..mu. is
the relative slot index of the slot or mini-slot where the channels
or signals are transmitted or received.
According to an example embodiment, in a spatial reuse (SR)
deployment scenario, different relative slot indices are used for
SR transmissions to improve inter-cell interference whitening at
UEs in different cells of the SR access nodes. In SR deployment
scenarios, the access nodes of the same operator network jointly
access the unlicensed channel. Therefore, the transmissions of the
SR access nodes overlap in the unlicensed time-frequency resources
with either aligned or unaligned transmission start. The overlap of
the unlicensed time-frequency resources can be realized by
alignment of the transmission start point or by delayed joint
channel access.
Due to the close proximity of the SR access nodes, scrambling or
hopping performance similar to that of 3GPP NR frequency reuse is
desired with unique scrambling or hopping sequences in concurrent
slots across the different cells of the SR access nodes. However,
in the system where SR transmissions are aligned at the start
point, these transmissions share the same reference slot. This
would result in the same relative slot indices being used to
generate the concurrent transmissions across the different cells of
the SR access nodes. Hence, the network or access node may need to
generate the concurrent SR transmissions using different relative
slot indices to improve the inter-cell interference whitening at
the UEs in the different cells of the SR access nodes.
The use of different relative slot indices for SR transmissions
allows 3GPP NR Unlicensed (NR-U) to harness the performance and
coexistence benefits of SR in the unlicensed spectrum with either
aligned or unaligned transmission start in different cells of the
SR access nodes. Also, networks have the flexibility to change
relative slot indices used for the generation of the downlink only
or shared COT with respect to the UE side configuration by
signaling a slot index offset so that the UE can apply the offset
to the relative slot index and thus properly descramble or decode
respective down link bursts, or generate uplink bursts.
Furthermore, scrambling or hopping performance similar to that of
3GPP NR frequency reuse (with unique scrambling or hopping
sequences) may be achieved in concurrent slots across inter-cell SR
access nodes, which are likely to be in close proximity to each
other. Additionally, the access node or network may be allowed to
generate intra-cell SR transmissions of unaligned start points
using the same relative slot indices over concurrent slots so that
the same scrambling or hopping sequences are used in the concurrent
slots of the intra-cell SR transmissions.
FIG. 12A illustrates example COTs transmitted by SR access nodes,
highlighting the use of different relative slot indices to improve
inter-cell interference whitening in a synchronous system. As shown
in FIG. 12A, a first COT 1205 is transmitted by a first SR access
node and a second COT 1207 is transmitted by a second SR access
node. First COT 1205 and second COT 1207 are transmitted
concurrently in the same slots starting from the same reference
slot. If relative slot indices are used, same relative slot indices
are going to be used across concurrent slots of the two COTs, and
thus inter-cell interference whitening would be degraded. However,
inter-cell interference whitening may be improved if different
relative slot indices are used for the two COTs, resulting in
different initial sequences or scrambling sequences. As an example,
first SR access node sets the reference slot index to zero for
transmissions of the first SR access node, and the reference slot
index for transmissions of the second SR access node is set to m,
where m is not equal to 0.
Because UEs are typically configured to assume that signals,
sequences and channels are prepared based on independent channel
access in which the default reference slot index is used, e.g.,
Slot #0, the downlink control field of an initial block may include
a Slot Index Offset that the UEs apply to the relative slot indices
for descrambling and decoding. If after applying the Slot Index
Offset to the relative slot indices, any of the new relative slot
indices exceed the maximum number of slots in a radio frame, a
cyclic shift (or a modulo operation) may be applied to the new
relative slot indices. As shown in FIG. 12, UEs receiving the COTs
apply respective relative slot indices for proper descrambling and
decoding. As an alternative to the Slot Index Offset, the relative
slot index may also be carried in the downlink control field. If
the relative slot index is not equal to zero, then the Slot Index
Offset is included in the downlink control field, for example.
FIG. 12B illustrates example COTs transmitted by SR access nodes,
highlighting the application of slot index offsets to relative slot
indices in order to align bursts. As shown in FIG. 12B, a first COT
1255 is transmitted by a first SR access node and a second COT 1257
is transmitted by a second SR access node. For discussion purposes,
consider a situation where the network sets the relative slot index
of the reference slot of COT 1257 to 5 and thus the relative slot
index of the second slot (Slot # m+1) is equal to 6. Then, even if
the relative slot index in the initial block indicates a value of
6, a UE receiving second COT 1257 does not know whether Slot #6 is
the second slot of second COT 1257 and that the slot index is
relative to the missed reference slot (Slot #.sub.5), or Slot #6 is
the first slot (the reference slot) of second COT 1257 with the
slot index starting at 6. The inclusion of the slot index offset
resolves the ambiguity. As an example, a slot index offset equal to
5 means that Slot #6 is the second slot of COT 1257 and that the
first reference of COT 1257 was missed, whereas a slot index offset
equal to 6 means that the slot is the first slot (the reference
slot) of COT 1257. Furthermore, if initial blocks cab be present
later in the COT, the UE may also assume that Slot #6 is the fourth
slot of COT 1257 wherein the first three slots were missed
including the reference slot with slot index 3. Indicating a slot
index offset equal to 5 confirms the latter case.
FIG. 13 illustrates example COTs transmitted by SR access nodes,
highlighting the use of different slot index offsets to facilitate
intra-cell SR transmissions to the same UE with unaligned
transmission start. When SR transmissions are not aligned at the
start point, they do not share the same reference slot. Therefore,
different relative slot indices would be normally used to generate
the concurrent transmissions across the different cells of the SR
access nodes. In some implementations, however, a UE may be served
by more than one access node utilizing SR in the unlicensed
channel. As shown in FIG. 13, a first COT 1305 is transmitted by a
first SR access node (AN1) and a second COT 1307 is transmitted by
a second SR access node (AN2). The first access node and the second
access node are of a single cell and are serving a UE. The access
nodes in such case may need to generate concurrent SR transmissions
using the same relative slot indices so that the same scrambling or
hopping sequences are used in the concurrent slots of the COTs. As
an example, the slot index offset for second COT 1307 is one
(instead of zero) to match the relative slot index of the same slot
of first COT 1305.
Because, as discussed previously, UEs are generally configured to
assume that signals and channels are prepared based on independent
channel access in which each access node starts transmission with a
default reference slot index, the network can use the downlink
control field of the initial block to include a Slot Index Offset
that the UEs apply to the relative slot indices for descrambling
and decoding of intra-cell SR transmissions. As shown in FIG. 13,
the downlink control field of the initial blocks of second SR
access node includes a Slot Index Offset value of one.
In some implementations, control overhead savings may be achieved
if the access node does not need to dynamically signal the Slot
Index Offsets to the respective UEs. Instead, the UEs can be
pre-configured with the respective Slot Index Offsets (in a
semi-static manner) for example, using higher-layer signaling, such
as radio resource control (RRC) signaling.
When some SR access nodes share the MCOT of one of them, the
initial blocks may include information of the MCOT so that the
transmission can end at the end point of the shared MCOT.
According to an example embodiment, in order to enable inter-cell
detection of COTs, initial blocks also include a PSS. In some
situations, it is beneficial to enable detection of COTs
transmitted by an access node of a cell by UEs or access nodes of
other cells. Such a feature can lead to improved coexistence and
spatial reuse. However, the initial blocks without the PSS may
enable only intra-cell detection (i.e., detection by UEs or access
nodes of the same cell). The inclusion of the PSS in the initial
blocks allows UEs or access nodes of other cells to attain full
time synchronization. However, the design of the initial block
should be unified, at least within the same network.
The presence of both the PSS and the SSS in the initial block may
lead to synchronization signal block (SSB) false detection by
initial access UEs because SSBs also include both PSS and SSS. In
order to avoid SSB false detection, one or more of the following
may be used: Reverse the order of multiplexing PSS and SSS used in
SSBs for the initial block. Reversing the multiplexing order
prevents UEs from potentially being able to distinguish the signals
prior to fully receiving the signals, requiring the UEs to store
the signals before being able to distinguish them. Use FDM to
multiplex the PSS and SSS on the same unlicensed channel. A
detecting access node or UE may need to store the signals before
the signals can be distinguished. Force the initial blocks to
occupy frequency resources that are shifted from those configured
for SSB transmission.
The inclusion of the PSS allows for inter-cell time
synchronization, allows NR-U to benefit from improved intra- or
inter-operator coexistence and spatial reuse, and avoids
performance degradation and failure or latency of initial access by
avoiding false detection of the initial blocks as SSBs by UEs
performing initial access.
FIG. 14 illustrates an example communication system 1400. In
general, the system 1400 enables multiple wireless or wired users
to transmit and receive data and other content. The system 1400 may
implement one or more channel access methods, such as code division
multiple access (CDMA), time division multiple access (TDMA),
frequency division multiple access (FDMA), orthogonal FDMA (OFDMA),
single-carrier FDMA (SC-FDMA), or non-orthogonal multiple access
(NoMA).
In this example, the communication system 1400 includes electronic
devices (ED) 1410a-1410c, radio access networks (RANs) 1420a-1420b,
a core network 1430, a public switched telephone network (PSTN)
1440, the Internet 1450, and other networks 1460. Although certain
numbers of these components or elements are shown in FIG. 14, any
number of these components or elements may be included in the
system 1400.
The EDs 1410a-1410c are configured to operate or communicate in the
system 1400. For example, the EDs 1410a-1410c are configured to
transmit or receive via wireless or wired communication channels.
Each ED 1410a-1410c represents any suitable end user device and may
include such devices (or may be referred to) as a user equipment or
device (UE), wireless transmit or receive unit (WTRU), mobile
station, fixed or mobile subscriber unit, cellular telephone,
personal digital assistant (PDA), smartphone, laptop, computer,
touchpad computer or device, wireless sensor, or consumer
electronics device.
The RANs 1420a-1420b here include base stations 1470a-1470b,
respectively. Each base station 1470a-1470b is configured to
wirelessly interface with one or more of the EDs 1410a-1410c to
enable access to the core network 1430, the PSTN 1440, the Internet
1450, or the other networks 1460. For example, the base stations
1470a-1470b may include (or be) one or more of several well-known
devices, such as a base transceiver station (BTS), a Node-B
(NodeB), an evolved NodeB (eNodeB), a Next Generation (NG) NodeB
(gNB), a Home NodeB, a Home eNodeB, a site controller, an access
point (AP), or a wireless router. The EDs 1410a-1410c are
configured to interface and communicate with the Internet 1450 and
may access the core network 1430, the PSTN 1440, or the other
networks 1460.
In the embodiment shown in FIG. 14, the base station 1470a forms
part of the RAN 1420a, which may include other base stations,
elements, or devices. Also, the base station 1470b forms part of
the RAN 1420b, which may include other base stations, elements, or
devices. Each base station 1470a-1470b operates to transmit or
receive wireless signals within a particular geographic region or
area, sometimes referred to as a "cell." In some embodiments,
multiple-input multiple-output (MIMO) technology may be employed
having multiple transceivers for each cell.
The base stations 1470a-1470b communicate with one or more of the
EDs 1410a-1410c over one or more air interfaces 1490 using wireless
communication links. The air interfaces 1490 may utilize any
suitable radio access technology.
It is contemplated that the system 1400 may use multiple channel
access functionality, including such schemes as described above. In
particular embodiments, the base stations and EDs implement 5G New
Radio (NR), LTE, LTE-A, or LTE-B. Of course, other multiple access
schemes and wireless protocols may be utilized.
The RANs 1420a-1420b are in communication with the core network
1430 to provide the EDs 1410a-1410c with voice, data, application,
Voice over Internet Protocol (VoIP), or other services.
Understandably, the RANs 1420a-1420b or the core network 1430 may
be in direct or indirect communication with one or more other RANs
(not shown). The core network 1430 may also serve as a gateway
access for other networks (such as the PSTN 144o, the Internet
1450, and the other networks 1460). In addition, some or all of the
EDs 1410a-1410c may include functionality for communicating with
different wireless networks over different wireless links using
different wireless technologies or protocols. Instead of wireless
communication (or in addition thereto), the EDs may communicate via
wired communication channels to a service provider or switch (not
shown), and to the Internet 1450.
Although FIG. 14 illustrates one example of a communication system,
various changes may be made to FIG. 14. For example, the
communication system 1400 could include any number of EDs, base
stations, networks, or other components in any suitable
configuration.
FIGS. 15A and 15B illustrate example devices that may implement the
methods and teachings according to this disclosure. In particular,
FIG. 15A illustrates an example ED 1510, and FIG. 15B illustrates
an example base station 1570. These components could be used in the
system 1400 or in any other suitable system.
As shown in FIG. 15A, the ED 1510 includes at least one processing
unit 1500. The processing unit 1500 implements various processing
operations of the ED 1510. For example, the processing unit 1500
could perform signal coding, data processing, power control,
input/output processing, or any other functionality enabling the ED
1510 to operate in the system 1400. The processing unit 1500 also
supports the methods and teachings described in more detail above.
Each processing unit 1500 includes any suitable processing or
computing device configured to perform one or more operations. Each
processing unit 1500 could, for example, include a microprocessor,
microcontroller, digital signal processor, field programmable gate
array, or application specific integrated circuit.
The ED 1510 also includes at least one transceiver 1502. The
transceiver 1502 is configured to modulate data or other content
for transmission by at least one antenna or NIC (Network Interface
Controller) 1504. The transceiver 1502 is also configured to
demodulate data or other content received by the at least one
antenna 1504. Each transceiver 1502 includes any suitable structure
for generating signals for wireless or wired transmission or
processing signals received wirelessly or by wire. Each antenna
1504 includes any suitable structure for transmitting or receiving
wireless or wired signals. One or multiple transceivers 1502 could
be used in the ED 1510, and one or multiple antennas 1504 could be
used in the ED 1510. Although shown as a single functional unit, a
transceiver 1502 could also be implemented using at least one
transmitter and at least one separate receiver.
The ED 1510 further includes one or more input/output devices 1506
or interfaces (such as a wired interface to the Internet 1450). The
input/output devices 1506 facilitate interaction with a user or
other devices (network communications) in the network. Each
input/output device 1506 includes any suitable structure for
providing information to or receiving information from a user, such
as a speaker, microphone, keypad, keyboard, display, or touch
screen, including network interface communications.
In addition, the ED 1510 includes at least one memory 1508. The
memory 1508 stores instructions and data used, generated, or
collected by the ED 1510. For example, the memory 1508 could store
software or firmware instructions executed by the processing
unit(s) 1500 and data used to reduce or eliminate interference in
incoming signals. Each memory 1508 includes any suitable volatile
or non-volatile storage and retrieval device(s). Any suitable type
of memory may be used, such as random access memory (RAM), read
only memory (ROM), hard disk, optical disc, subscriber identity
module (SIM) card, memory stick, secure digital (SD) memory card,
and the like.
As shown in FIG. 15B, the base station 1570 includes at least one
processing unit 1550, at least one transceiver 1552, which includes
functionality for a transmitter and a receiver, one or more
antennas 1556, at least one memory 1558, and one or more
input/output devices or interfaces 1566. A scheduler, which would
be understood by one skilled in the art, is coupled to the
processing unit 1550. The scheduler could be included within or
operated separately from the base station 1570. The processing unit
1550 implements various processing operations of the base station
1570, such as signal coding, data processing, power control,
input/output processing, or any other functionality. The processing
unit 1550 can also support the methods and teachings described in
more detail above. Each processing unit 1550 includes any suitable
processing or computing device configured to perform one or more
operations. Each processing unit 1550 could, for example, include a
microprocessor, microcontroller, digital signal processor, field
programmable gate array, or application specific integrated
circuit.
Each transceiver 1552 includes any suitable structure for
generating signals for wireless or wired transmission to one or
more EDs or other devices. Each transceiver 1552 further includes
any suitable structure for processing signals received wirelessly
or by wire from one or more EDs or other devices. Although shown
combined as a transceiver 1552, a transmitter and a receiver could
be separate components. Each antenna 1556 includes any suitable
structure for transmitting or receiving wireless or wired signals.
Although a common antenna 1556 is shown here as being coupled to
the transceiver 1552, one or more antennas 1556 could be coupled to
the transceiver(s) 1552, allowing separate antennas 1556 to be
coupled to the transmitter and the receiver if equipped as separate
components. Each memory 1558 includes any suitable volatile or
non-volatile storage and retrieval device(s). Each input/output
device 1566 facilitates interaction with a user or other devices
(network communications) in the network. Each input/output device
1566 includes any suitable structure for providing information to
or receiving/providing information from a user, including network
interface communications.
FIG. 16 is a block diagram of a computing system 1600 that may be
used for implementing the devices and methods disclosed herein. For
example, the computing system can be any entity of UE, access
network (AN), mobility management (MM), session management (SM),
user plane gateway (UPGW), or access stratum (AS). Specific devices
may utilize all of the components shown or only a subset of the
components, and levels of integration may vary from device to
device. Furthermore, a device may contain multiple instances of a
component, such as multiple processing units, processors, memories,
transmitters, receivers, etc. The computing system 1600 includes a
processing unit 1602. The processing unit includes a central
processing unit (CPU) 1614, memory 1608, and may further include a
mass storage device 1604, a video adapter 1610, and an I/O
interface 1612 connected to a bus 1620.
The bus 1620 may be one or more of any type of several bus
architectures including a memory bus or memory controller, a
peripheral bus, or a video bus. The CPU 1614 may comprise any type
of electronic data processor. The memory 1608 may comprise any type
of non-transitory system memory such as static random access memory
(SRAM), dynamic random access memory (DRAM), synchronous DRAM
(SDRAM), read-only memory (ROM), or a combination thereof. In an
embodiment, the memory 1608 may include ROM for use at boot-up, and
DRAM for program and data storage for use while executing
programs.
The mass storage 1604 may comprise any type of non-transitory
storage device configured to store data, programs, and other
information and to make the data, programs, and other information
accessible via the bus 1620. The mass storage 1604 may comprise,
for example, one or more of a solid state drive, hard disk drive, a
magnetic disk drive, or an optical disk drive.
The video adapter 1610 and the I/O interface 1612 provide
interfaces to couple external input and output devices to the
processing unit 1602. As illustrated, examples of input and output
devices include a display 1618 coupled to the video adapter 1610
and a mouse, keyboard, or printer 1616 coupled to the I/O interface
1612. Other devices may be coupled to the processing unit 1602, and
additional or fewer interface cards may be utilized. For example, a
serial interface such as Universal Serial Bus (USB) (not shown) may
be used to provide an interface for an external device.
The processing unit 1602 also includes one or more network
interfaces 1606, which may comprise wired links, such as an
Ethernet cable, or wireless links to access nodes or different
networks. The network interfaces 1606 allow the processing unit
1602 to communicate with remote units via the networks. For
example, the network interfaces 1606 may provide wireless
communication via one or more transmitters/transmit antennas and
one or more receivers/receive antennas. In an embodiment, the
processing unit 1602 is coupled to a local-area network 1622 or a
wide-area network for data processing and communications with
remote devices, such as other processing units, the Internet, or
remote storage facilities.
FIG. 17 illustrates a flow diagram of example operations 1700
occurring in an access node performing a transmission that involves
a LBT failure. Operations 170o may be indicative of operations
occurring in an access node as the access node performs a
transmission that involves a LBT failure.
Operations 1700 begin with the access node generating an initial
block (block 1705). The initial block includes a time-independent
initial sequence. The access node performs a LBT procedure and
determines that the shared communications channel is unavailable
during a first slot (block 1707). The access node waits and tries
the LBT procedure again during a second slot and determines that
the shared communications channel is available during a second slot
and transmits the initial block (block 1709). The access node did
not have to regenerate the initial block due to the initial block
including the time-independent initial sequence.
The following examples may assist in understanding the present
disclosure:
Example 1
A computer-implemented method for operating an access node, the
method comprising: generating, by the access node, an initial block
and a time-dependent signal for transmission in a channel occupancy
time (COT) of a shared communications channel, the initial block
including a time-independent initial sequence that enables the
initial block to be transmitted over any slot in the COT, wherein
the time-dependent signal is transmitted after the initial block;
and transmitting, by the access node, the initial block and the
time-dependent signal in the COT.
Example 2
The method of Example 1, wherein the initial block identifies the
slot within which it is transmitted as a reference slot.
Example 3
The method of Example 2, wherein the time-dependent signal is
time-dependent relative to a time of the reference slot.
Example 4
The method of Example 1, wherein the initial block further
comprises control information configuring the COT.
Example 5
The method of Example 4, wherein the control information comprises
at least one of an indicator of a duration of the COT, or an
indicator of a composition of the COT.
Example 6
The method of Example 5, wherein the indicator of the composition
of the COT comprises a transmission type for each slot of the
COT.
Example 7
The method of Example 4, wherein the relative slot index of the
slot where the initial block located is carried in the control
information field of the initial block.
Example 8
The method of Example 7, further comprising adjusting, by the
access node, the relative slot index of the slot with a slot offset
associated with the COT.
Example 9
The method of Example 1, wherein the time-independent initial
sequence comprises a secondary synchronization signal (SSS) or a
demodulation reference signal (DMRS) for a control information.
Example 10
The method of Example 9, wherein the control information is carried
in a physical layer channel with a structure of a physical
broadcast channel (PBCH), or in a physical downlink control channel
(PDCCH) with a structure of control resource set (CORESET).
Example 11
The method of Example 9, wherein the time-independent initial
sequence further comprises a primary synchronization signal
(PSS).
Example 12
The method of Example 1, wherein there is a plurality of initial
blocks, wherein the shared communications channel comprises a
plurality of carriers, and wherein at least one initial block of
the plurality of initial blocks is transmitted in a subset of
carriers of the plurality of carriers.
Example 13
The method of Example 12, wherein the initial blocks transmitted in
the subset of carriers during a slot are different.
Example 14
The method of Example 12, wherein the initial blocks transmitted in
the subset of carriers during a slot are duplicates.
Example 15
The method of Example 1, wherein there is a plurality of initial
blocks transmitted in the COT, wherein a first subset of the
plurality of initial blocks are transmitted in a first subset of
slots of the COT, and a second subset of the plurality of initial
blocks are transmitted in a second subset of the slots of the
COT.
Example 16
The method of Example 15, wherein each ones of the first subset of
the plurality of initial blocks comprise a time-independent initial
sequence, and each ones of the second subset of the plurality of
initial blocks comprise a time-independent initial sequence and
control information configuring the COT.
Example 17
The method of Example 1, wherein the time-independent initial
sequence of the initial block comprises a plurality of duplicates
of a SSS or a DMRS PBCH.
Example 18
The method of Example 1, further comprising transmitting, by the
access node, a transmission in a slot during a downlink portion of
the COT, wherein the transmission is scrambled in accordance with a
relative slot index of the slot.
Example 19
A computer-implemented method for operating a user equipment (UE),
the method comprising:
detecting, by the UE on a shared communications channel, an initial
block and a time-dependent signal, where the initial block includes
a time-independent initial sequence, and wherein the time-dependent
signal is detected after the initial block is detected; and
identifying, by the UE, a slot of a channel occupancy time (COT) of
the shared communications channel wherein the initial block was
detected as a reference slot.
Example 20
The method of Example 19, further comprising receiving, by the UE,
a transmission in a slot during a downlink portion of the COT,
wherein the transmission is scrambled in accordance with the
reference slot and a relative slot index of the slot.
Example 21
The method of Example 19, wherein the initial block further
comprises control information configuring the COT.
Example 22
The method of Example 21, wherein the control information comprises
at least one of an indicator of a duration of the COT, or an
indicator of a composition of the COT.
Example 23
The method of Example 21, wherein the relative slot index of the
slot where the initial block located is carried in the control
information field of the initial block.
Example 24. The method of Example 23, further comprising adjusting,
by the UE, the relative slot index of the reference slot with a
slot offset associated with the COT.
Example 25
The method of Example 19, wherein the time-independent initial
sequence comprises a secondary synchronization signal (SSS) or a
demodulation reference signal (DMRS) for a control information.
Example 26
The method of Example 25, wherein the control information is
carried in a physical layer channel with a structure of a physical
broadcast channel (PBCH), or in a physical downlink control channel
(PDCCH) with a structure of control resource set (CORESET).
Example 27
The method of Example 25, wherein the time-independent initial
sequence further comprises a primary synchronization signal
(PSS).
Example 28
The method of Example 19, wherein there is a plurality of initial
blocks, wherein the shared communications channel comprises a
plurality of carriers, and wherein at least one initial block of
the plurality of initial blocks is transmitted in a subset of
carriers of the plurality of carriers.
Example 29
The method of Example 28, wherein the initial blocks received in
the subset of carriers during a slot are different.
Example 30
The method of Example 28, wherein the initial blocks received in
the subset of carriers during a slot are duplicates.
Example 31
The method of Example 19, wherein there is a plurality of initial
blocks are detected in the COT, wherein a first subset of the
plurality of initial blocks are received in a first subset of slots
of the COT, and a second subset of the plurality of initial blocks
are received in a second subset of the slots of the COT.
Example 32
The method of Example 31, wherein each ones of the first subset of
the plurality of initial blocks comprise a time-independent initial
sequence, and each ones of the second subset of the plurality of
initial blocks comprise a time-independent initial sequence and
control information configuring the COT.
Example 33
The method of Example 19, wherein the time-independent initial
sequence of the initial block comprises a plurality of duplicates
of a SSS or a DMRS PBCH.
Example 34
The method of Example 19, further comprising receiving, by the UE,
a transmission in a slot during a downlink portion of the COT,
wherein the transmission is scrambled in accordance with a relative
slot index of the slot.
Example 35
A computer-implemented method for operating an access node, the
method comprising:
generating, by the access node, an initial block for a channel
occupancy time (COT) of a shared communications channel, the
initial block comprising a time-independent initial sequence;
determining, by the access node, that the shared communications
channel is unavailable at a first slot; and
transmitting, by the access node, the initial block for the COT in
a second slot without regenerating the initial block.
Example 36
The method of Example 35, wherein the initial block further
comprises control information configuring the COT.
Example 37
The method of Example 36, wherein the time-independent initial
sequence of the initial block is scrambled with a scrambling
sequence initialized with a relative slot index of a slot where the
initial block is transmitted.
Example 38
The method of Example 37, further comprising adjusting, by the
access node, the relative slot index of the second slot with a slot
offset associated with the COT.
It should be appreciated that one or more steps of the embodiment
methods provided herein may be performed by corresponding units or
modules. For example, a signal may be transmitted by a transmitting
unit or a transmitting module. A signal may be received by a
receiving unit or a receiving module. A signal may be processed by
a processing unit or a processing module. Other steps may be
performed by a generating unit or module, or an adjusting unit or
module. The respective units or modules may be hardware, software,
or a combination thereof. For instance, one or more of the units or
modules may be an integrated circuit, such as field programmable
gate arrays (FPGAs) or application-specific integrated circuits
(ASICs).
Although the present disclosure and its advantages have been
described in detail, it should be understood that various changes,
substitutions and alterations can be made herein without departing
from the scope of the disclosure as defined by the appended
claims.
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